JP3918911B2 - Rotation angle detection device, audio playback device, and head-mounted display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotation angle detection device using an angular velocity sensor that detects a rotation angular velocity of a detection target, and an electronic apparatus such as a sound reproduction device and a head-mounted display device including the rotation angle detection device.
[0002]
[Prior art]
Integrating the angular velocity detection signal output from the angular velocity sensor to detect the rotation angle (rotation angle) of the detection target is performed and considered in various fields.
[0003]
For example, by attaching an angular velocity sensor to headphones, detecting the rotation of the head of the listener wearing the headphones, and processing the audio signal according to the detection result, even if the listener is directed in the left and right direction, It is considered that the sound image is localized at an arbitrary fixed position outside the listener's head so that a sound field equivalent to that obtained when a speaker is disposed at that position can be obtained.
[0004]
In the car navigation system, a correct traveling direction is calculated by detecting a change in the traveling direction of the vehicle, and a GPS (Global Positioning System) that knows the position by using this and the output of the vehicle speed sensor or by using a satellite. Is used together to calculate the current position.
[0005]
However, the angular velocity detection signal output from the angular velocity sensor includes an extremely low frequency component close to direct current as an offset component, and the level of the offset component varies from one angular velocity sensor to another. Fluctuates due to environmental changes.
[0006]
Therefore, when the angular velocity detection signal output from the angular velocity sensor is integrated as it is to detect the rotation angle, the detected object is detected as rotating even when the detected object is stationary, and the detected object rotates. Even during this time, the rotation angle cannot be detected accurately. Therefore, it is necessary to remove this offset component from the angular velocity detection signal output from the angular velocity sensor.
[0007]
FIG. 6 shows a conventional rotation angle detection device for removing this offset component. In this rotation angle detection device, the output signal of the angular velocity sensor 10 is converted into digital data by the A / D converter 21 and taken out through the low-pass filter 22. The low-pass filter 22 extracts a necessary band component from the output signal of the angular velocity sensor 10, and has a cutoff frequency of, for example, 100 Hz.
[0008]
The angular velocity detection signal Do extracted from the low-pass filter 22 is supplied to the high-pass filter 101, and low-frequency components that are offset components are removed. The cutoff frequency of the high pass filter 101 is, for example, 0.01 Hz.
[0009]
However, when the angular velocity detection signal Do is taken out through the high-pass filter 101 in order to remove the offset component, a backlash B is generated in the angular velocity detection signal Dp output from the high-pass filter 101 as shown in FIG. When integrated with, it becomes a big error.
[0010]
Therefore, the angular velocity detection signal Dp output from the high-pass filter 101 is supplied to the low level removal circuit 102, and the low level signal indicated by the level range L in FIG. 7 in the angular velocity detection signal Dp is removed. The angular velocity detection signal Dq is integrated by the integration circuit 103.
[0011]
[Problems to be solved by the invention]
However, in the conventional rotation angle detection device of FIG. 6, since the offset component is removed from the original angular velocity detection signal Do by the high-pass filter 101, the backlash B is generated in the angular velocity detection signal Dp after the offset component is removed. In order to remove the backlash B, the low level removal circuit 102 removes the low level signal in the angular velocity detection signal Dp after the offset component has been removed. Therefore, some of the angular velocity detection components that are not offset components have also been lost. Thus, the rotation angle cannot be detected with high accuracy.
[0012]
The time constant of the high-pass filter 101 is increased to suppress the backlash B, and the angular velocity detection signal Dp output from the high-pass filter 101 is directly integrated by the integration circuit 103 without removing the low-level signal by the low-level removal circuit 102. It is also possible. However, in that case, it takes time for the high-pass filter 101 to reach a steady state, and during that time, the offset component cannot be removed and the rotation angle cannot be detected.
[0013]
Therefore, the present invention is configured to detect a rotation angle with high accuracy in a rotation angle detection device using an angular velocity sensor.
[0014]
[Means for Solving the Problems]
The rotation angle detection device of the present invention comprises:
A low-pass filter that detects a low-frequency component from an output signal of an angular velocity sensor that detects the rotational angular velocity of the detected object;
A storage unit in which the detected low frequency component is written as an offset value for a plurality of samples, and
A rotation determining unit that determines whether or not the detected object is rotating from an output signal of the angular velocity sensor;
When the rotation determining unit determines that the detected object is not rotating, the low frequency component detected by the low-pass filter is written in the storage unit as an offset value, and the rotation determining unit detects the detected object. A controller that stops writing low-frequency components to the storage unit and reads offset values for a plurality of samples from the storage unit,
An average value of offset values for a plurality of samples read from the storage unit, a calculation unit that subtracts the calculation result from the output signal of the angular velocity sensor, and integrates the subtraction result;
Shall be provided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment of Rotation Angle Detection Device ... FIGS. 1 and 2]
FIG. 1 shows an embodiment of a rotation angle detection device of the present invention.
[0016]
An angular velocity sensor 10 such as a piezoelectric vibration gyro that detects the rotational angular velocity is attached to the detection object 1. The angular velocity detection signal output from the angular velocity sensor 10 includes a component having a very low frequency close to DC as an offset component, and the level of the offset component varies from one angular velocity sensor to another, such as temperature. It fluctuates due to environmental changes.
[0017]
The output signal of the angular velocity sensor 10 is converted into digital data by the A / D converter 21 and taken out through the low-pass filter 22. The low-pass filter 22 extracts a necessary band component from the output signal of the angular velocity sensor 10, and its cutoff frequency is set to 100 Hz, for example.
[0018]
The angular velocity detection signal Do extracted from the low-pass filter 22 is supplied to a low-pass filter 31 in the offset detection unit 30 to detect a low frequency component. The cutoff frequency of the low-pass filter 31 is selected within the range of 0.125 Hz to 0.002 Hz, for example.
[0019]
At the same time, the angular velocity detection signal Do extracted from the low-pass filter 22 is supplied to the rotation determination unit 32 in the offset detection unit 30, and the rotation determination unit 32 determines the detected object 1 from the degree of change in the angular velocity detection signal Do. It is determined whether or not is rotating.
[0020]
Specifically, the rotation determination unit 32 compares the sample value with the immediately preceding sample value for each sample of the angular velocity detection signal Do that is digital data, and the change between the two is within a predetermined threshold value. The rotation determination unit 32 is configured to determine that the detection target 1 is stationary and to determine that the detection target 1 is rotating when the change between the two exceeds a predetermined threshold.
[0021]
The determination result of the rotation determination unit 32 is supplied to the buffer control unit 33. When the rotation control unit 32 determines that the detection target 1 is stationary, the buffer control unit 33 uses the low-pass filter 31 at that time. The detected low frequency component is written in the ring buffer 34 as an offset value.
[0022]
For example, as shown in FIG. 2, the ring buffer 34 can write offset values for up to 16 samples. When 16 samples are written, the oldest one is erased and the new one is written. Configure.
[0023]
When the rotation determining unit 32 determines that the detection target 1 is rotating, the buffer control unit 33 stops writing the low-frequency component detected by the low-pass filter 31 to the ring buffer 34 at that time. The offset value for a maximum of 16 samples written in the buffer 34 is read out.
[0024]
Then, the averaging processing unit 35 calculates an average value of offset values for a maximum of 16 samples read from the ring buffer 34, and the adding circuit 40 generates a signal Ds as a calculation result of the averaging processing unit 35. The integration circuit 51 subtracts the subtracted signal Dv from the angular velocity detection signal Do as an offset component in the angular velocity detection signal Do from the low-pass filter 22 of the signal detector 20 and uses the resulting signal Dv as the angular velocity detection signal after the offset component is removed. Integrate with.
[0025]
The low-frequency component detected by the low-pass filter 31 when the detection object 1 is stationary is an angular velocity detection signal output from the angular velocity sensor 10 regardless of variations among the angular velocity sensors or changes in the environment such as temperature. In contrast to the offset component in Do, the low frequency component detected by the low pass filter 31 when the detection object 1 is rotating includes an angular velocity detection component and does not match the offset component.
[0026]
In the rotation angle detection device described above, only the low frequency component equal to the offset component when the detected object 1 is stationary is written in the ring buffer 34, and when the detected object 1 is rotating, The low frequency component when the detected object 1 is stationary is read from the ring buffer 34, and the average value is subtracted from the angular velocity detection signal Do of the output of the angular velocity sensor 10, so that the offset component is reliably and accurately obtained. The rotation angle can be detected with high accuracy.
[0027]
The time constant of the low-pass filter 31 can be changed by the control signal Sc, and the time constant is reduced at the start of operation of the electronic apparatus including the detection target 1 and provided with the rotation angle detection device, such as when the power is turned on. Thereafter, the time constant is gradually increased.
[0028]
As a result, when the operation of the electronic device is started, the low-pass filter 31 can be converged to a stable state in a short time, and high-precision detection of the rotation angle can be started in a short time.
[0029]
In the output processing unit 50, the rotation angle detection signal output from the integration circuit 51 is supplied to the azimuth conversion unit 52 as necessary, and the rotation direction and the rotation angle with respect to the reference azimuth of the detection target 1 are detected. Detected as one direction.
[0030]
[Embodiment of Audio Reproducing Device ... FIGS. 3 and 4]
The rotation angle detection device of the present invention can be used, for example, in a sound reproducing device that listens to sound using headphones and localizes a sound image at an arbitrary fixed position outside the listener's head.
[0031]
FIG. 3 shows the principle, in which the listener 3 wears the headphones 5 and listens to the sound by the left and right acoustic transducers 5L and 5R, and the sound image of the sound signal is obtained even if the listener 3 is directed in the left and right directions. For example, a sound field equivalent to the case where a speaker is disposed at a position indicated by the sound source 7 on the median plane in front of the listener is obtained. In this case, the transfer functions from the sound source 7 to the left ear 3L and the right ear 3R of the listener 3 are HL and HR.
[0032]
FIG. 4 shows an embodiment of the sound reproducing apparatus of the present invention in this case. An angular velocity sensor 10 is attached to the headphone 5, and an output signal of the angular velocity sensor 10 is detected as a rotation angle of the configuration shown in FIG. Supplied to the device 60 to detect the rotation of the head of the listener wearing the headphones 5.
[0033]
In this case, the output processing unit 50 of the rotation angle detection device 60 detects the rotation direction and rotation angle of the listener head direction (direction) θ from the direction θ0 of the sound source 7 in FIG. To.
[0034]
In this embodiment, the transfer functions HL (θ0) and HL (θ1) from the sound source 7 in FIG. 3 to the left ear 3L of the listener 3 when the listener head direction θ is θ0, θ1, θ2,. ), HL (θ2),... HL (θn) and the transfer functions HR (θ0), HR (θ1), HR (θ2),... HR (θn) from the sound source 7 to the right ear 3R of the listener 3 Digital filters 71-0, 71-1, 71-2,... 71-n and 72-0, 72-1, 72-2,. Are supplied to the digital filters 71-0, 71-1, 71-2, ... 71-n and 72-0, 72-1, 72-2, ... 72-n. θ1, θ2,... θn are set at equiangular intervals in the clockwise direction and the counterclockwise direction from the direction of θ0.
[0035]
Then, the orientation of the listener head at that time indicated by the detection signal from the rotation angle detection device 60 among the digital filters 71-0, 71-1, 71-2, ... 71-n by the selector 73L. The output signal of the filter corresponding to the azimuth closest to θ is taken out as an audio signal to be supplied to the acoustic transducer 5L on the left side of the headphone 5, and the digital filters 72-0, 72-1, 72-2 are selected by the selector 73R. ,... 72-n, the output signal of the filter corresponding to the direction closest to the direction θ of the listener's head indicated by the detection signal from the rotation angle detection device 60 is Extracted as an audio signal to be supplied to the acoustic transducer 5R.
[0036]
The digital audio signals output from the selectors 73L and 73R are converted into analog audio signals by the D / A converters 74L and 74R, and the two analog audio signals are amplified by the audio amplifier circuits 75L and 75R. The left and right acoustic transducers 5L and 5R are supplied.
[0037]
In this case, the rotation angle detection device 60 does not detect the low-frequency component until the low-pass filter 31 shown in FIG. A detection signal cannot be obtained, and the sound image of the audio signal Di is not localized at the desired position.
[0038]
Therefore, the audio amplification circuits 75L and 75R are controlled by the control signal Sc, and until the low frequency component is detected by the low-pass filter 31 shown in FIG. Makes the audio output silent.
[0039]
[Embodiment of Head Mounted Display Device ... FIG. 5]
The rotation angle detection device of the present invention can be used, for example, in a head-mounted display device, so-called HMD (Head Mounted Display).
[0040]
FIG. 5 shows an embodiment of the head-mounted display device of the present invention. The head mounting portion 81 of the head mounted display device includes a main body portion 82 that is located in front of the user 9 and arm portions 83L and 83R that put it on the user 9's ears. Video display portions 85L and 85R such as a panel are provided.
[0041]
The angular velocity sensor 10 is attached to the head mounting portion 81, and the rotation angle detecting device 60 having the configuration shown in FIG. 1 is provided to detect the rotation of the user's head wearing the head mounting portion 81.
[0042]
In this case, the output processing unit 50 of the rotation angle detection device 60 detects the rotation direction and rotation angle of the orientation (direction) of the user's head at that time from the orientation of the front of the user 9 in FIG. So that
[0043]
On the other hand, the digital video signals SL and SR obtained at the input terminals 91L and 91R are supplied to the video processing units 92L and 92R.
[0044]
The video processing units 92L and 92R include an image memory, and control the writing of the video signals SL and SR to the image memory and the reading from the image memory by a detection signal from the rotation angle detection device 60, which will be described later. As described above, the video displayed on the video display units 85L and 85R of the head-mounted unit 81 can be moved in the left-right direction on the respective display screens 86L and 86R.
[0045]
The video signals from the video processing units 92L and 92R are converted into analog video signals by the D / A converters 93L and 93R, and the analog video signals are supplied to the display driving units 94L and 94R. The display driving units 94L and 94R The video display units 85L and 85R are driven.
[0046]
When the user 9 turns from the front side as shown in FIG. 5 to the left side, the use on the display screens 86L and 86R of the video display units 85L and 85R is performed by the processing in the video processing units 92L and 92R. When the user 9 turns to the right from the front side as shown in FIG. 5, the video is displayed at the position moved to the right according to the rotation angle of the head of the person. By the processing in the video processing units 92L and 92R, the video is displayed on the display screens 86L and 86R of the video display units 85L and 85R at positions moved to the left according to the rotation angle of the user's head. Like that.
[0047]
As a result, the user 9 is displaying the image at a fixed position on the front even when facing the left and right direction with the head mounting portion 81 provided with the image display portions 85L and 85R mounted. As you can see the picture.
[0048]
In this case, the rotation angle detection device until the low-frequency component is detected by the low-pass filter 31 shown in FIG. 1 of the rotation angle detection device 60 at the start of operation such as when the head-mounted display device is turned on. An accurate detection signal cannot be obtained from 60, and the virtual video display position cannot be determined as the intended position.
[0049]
Therefore, the video processing units 92L and 92R are controlled by the control signal Sc, and the low-frequency component is detected by the low-pass filter 31 shown in FIG. 1 of the rotation angle detection device 60 when the head-mounted display device starts operating. Until the video display position is not moved on the display screens 86L and 86R, the display screen 86L and 86R are stopped, or a warning that the operation is unstable is displayed on the display screens 86L and 86R.
[0050]
When the head-mounted display device of this embodiment is combined with the audio playback device of the embodiment shown in FIG. 4, an image is always displayed at a fixed position in the viewing environment even when the viewer is directed in the left-right direction. It is possible to construct a video / audio reproduction system in which a video can be viewed as displayed and a sound image is localized at a certain position in the viewing environment.
[0051]
【The invention's effect】
As described above, according to the present invention, the rotation angle can be detected with high accuracy in the rotation angle detection device using the angular velocity sensor.
[0052]
In addition, the time constant of the low-pass filter for detecting low-frequency components is relatively small at the start of device operation, and then relatively large, so that the low-pass filter can be stabilized in a short time at the start of device operation. It is possible to converge to the state, and to start the detection of the rotation angle with high accuracy in a short time.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a rotation angle detection device of the present invention.
FIG. 2 is a diagram showing a part of the rotation angle detection device of FIG. 1;
FIG. 3 is a diagram for explaining the case where a sound image is localized at a position outside the listener's head.
FIG. 4 is a diagram showing an embodiment of an audio playback device of the present invention.
FIG. 5 is a diagram showing an embodiment of a head mounted display device according to the present invention.
FIG. 6 is a diagram illustrating a conventional rotation angle detection device.
7 is a diagram for explaining the rotation angle detection device of FIG. 6;
[Explanation of symbols]
Since all the main parts are described in the figure, they are omitted here.

Claims (7)

A low-pass filter that detects a low-frequency component from an output signal of an angular velocity sensor that detects a rotational angular velocity of the detected object;
A storage unit in which the detected low frequency component is written as a plurality of samples as an offset value;
A rotation determining unit that determines whether or not the detected object is rotating from an output signal of the angular velocity sensor;
When the rotation determining unit determines that the detected object is not rotating, the low frequency component detected by the low-pass filter is written in the storage unit as an offset value, and the rotation determining unit detects the detected object. A controller that stops writing low-frequency components to the storage unit and reads offset values for a plurality of samples from the storage unit,
An average value of offset values for a plurality of samples read from the storage unit, a calculation unit that subtracts the calculation result from the output signal of the angular velocity sensor, and integrates the subtraction result;
A rotation angle detection device comprising: In the rotation angle detection apparatus of Claim 1,
A rotation angle detection device in which the time constant of the low-pass filter is relatively reduced at the start of operation of the device and then relatively increased. 3. A sound reproduction device comprising the rotation angle detection device according to claim 1 or 2, wherein the angular velocity sensor is attached to a headphone, and the sound signal is controlled by an output signal of the rotation angle detection device. The sound reproducing device according to claim 3,
A sound reproducing device in which sound output is silenced at the start of operation of the device until a low frequency component is detected by the low-pass filter of the rotation angle detecting device. A head-mounted display device comprising the rotation angle detection device according to claim 1, wherein the angular velocity sensor is attached to the head mounting portion, and the head mounting portion is determined by an output signal of the rotation angle detection device. A head-mounted display device in which video display on a video display unit provided in the head is controlled. The head-mounted display device according to claim 5,
At the start of the operation of the device, the video display position is stopped on the video display unit or a warning is displayed on the video display unit until the low-frequency component is detected by the low-pass filter of the rotation angle detection device. Head mounted display device to be displayed. An electronic device comprising the rotation angle detection device according to claim 1.

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